The present invention relates generally to rotational control apparatuses such as clutches or brakes, particularly to cooling such apparatus, also particularly to drive discs which may be utilized in such rotational control apparatuses, and to ventilated hubs and ventilated friction discs which can be utilized in drive discs of such rotational control apparatuses.
It is a continuous problem to provide clutches or brakes which are efficient, and which have high ability to transfer the heat energy generated in the engagement process and/or in a constant slipping arrangement. The ability to transfer heat energy is especially desired in drive discs utilized in rotational control apparatuses where force must be transferred through the drive disc rather than just the outside of the drive disc. Further, the ability to thermally insulate the piston from the pressure plate in a simple, economic manner is also highly desired in rotational control apparatuses.